The present invention relates to a cleaning tool intended for use in downhole environments.
After casing or liner has been run into a well bore and cemented in place, it is conventional to use a cleaning tool to clean the interior of the casing or liner and to remove any obstructions such as burrs or lumps of cement which may be remnant from the cementing procedure. Conventional cleaning tools usually take one of two forms which are well known in the art. Brushing tools are afforded a bed of bristles on their exterior surface which xe2x80x9cbrushxe2x80x9d the casing or liner surface while casing scrapers incorporate blades, typically made of steel, which scrape the interior surface of the casing or liner. The blades or brushes are often mounted on supporting pads which are typically biased outwardly by coil springs to encourage contact between the cleaning member and the casing or liner surface.
This invention relates to improvements to our earlier British Patent Application Number 9917601.8 which teaches of a downhole tool comprised of a housing which is typically an upper and lower sleeve which can be mounted on a work string and which support at least one floating component. The floating component, which is a lantern or the like, supports cleaning members such as brushes or scraper blades and can move in a lateral or radial position within receptive components present in the housing. This negates the requirement for springs which are typically used to impart an outward radial bias to the cleaning members on conventional cleaning tools and have been known to break off. In addition superior cleaning properties are afforded to the cleaning tool, as the cleaning members mounted on the lanterns can make more frequent contact with the casing or liner than conventional tools, as the tool remains centralised within the bore. This is particularly important when the casing or liner lines a well which is deviated or horizontal.
Whilst this arrangement increases the efficiency of the cleaning procedure, the friction created when the lantern contacts the casing or liner holds the lantern in a stationary position from a rotational perspective. It would be a distinct advantage to provide a cleaning tool wherein the lantern rotates in synchrony with the work string in order to further increase the efficiency of the cleaning procedure. However continuous rotation of the lantern which holds the cleaning members, particularly if the cleaning members were scraper blades, could actually wear the casing. Consequently, the damaged casing would have to be replaced, necessitating the implementation of costly, difficult and timely procedures. It would therefore be advantageous to provide a cleaning tool wherein the lantern which carries the cleaning members rotates in Synchrony with the work string when desired, but has no or negligible rotational movement, at other times.
Furthermore, in the event that the lantern carrying the cleaning members meets an obstruction, the resultant torque, or resistance to rotation, may be sufficient to deform the lantern. It would therefore be a distinct advantage to provide a cleaning tool with the superior cleaning abilities of the tool disclosed in British Patent Application Number 9917601.8, but which can rotate in synchrony with the work string if required, without risk of seizing or deforming under excessive load.
It is an object of the present invention to provide an improved cleaning tool for cleaning casing in a downhole environment.
It is a further object of the present invention to provide a cleaning tool comprising means for transferring the rotational movement of the work string to the cleaning members, wherein the transferring means will shear or rupture if the resistance to the tool exceeds a given load.
It is a yet further object of the present invention to provide a cleaning tool wherein the lantern which supports the cleaning members can rotate in synchrony with the work string when desired, but can also not rotate when required.
According to the present invention there is provided a cleaning tool for mounting on a work string, the cleaning tool being comprised of an upper and lower sleeve and a floating component located between the sleeves, wherein the floating component is free to move in a radial direction relative to the work string within predetermined limits set by the upper and lower sleeve, and wherein the floating component is mechanically linked to the work string by a rupture means, wherein the rupture means is adapted to rupture if the torque or resistance to rotational movement of the floating component exceeds a predetermined load, and wherein upon breaking of the rupture means the floating component will be allowed to have no or negligible rotational movement.
Preferably the rupture means is a shear pin.
Preferably, at least one of the upper and lower sleeve comprises a clutch which engages with the floating component.
Preferably the clutch is held to the work string by the rupture means.
Preferably the upper and lower sleeve have female receiving means for receiving the floating component.
Most preferably the female receiving means have a greater external diameter than the floating component.
Typically the floating component may move axially relative to the work string between a first position whereat it engages the clutch and a second position where it does not so engage the clutch.
Preferably the upper and lower sleeve are mounted by ball bearings that allow for the work string to rotate relative to the upper and lower sleeve.
Preferably the upper and lower sleeve act as stabilisers for the work string in the well bore.
Typically the floating component supports a plurality of cleaning members.
Optionally the cleaning members are brushes. Alternatively the cleaning members may be scraper blades.
Preferably the floating component is a lantern or the like.
Optionally the floating component may be provided with elongate slots which afford flexibilty to the floating component.
An example embodiment of the invention will now be illustrated with reference to the following Figures in which: